A drilling device is, in general, employed for the purposes of drilling holes to collect underground resources or for civil engineering construction. In particular, a rotary type drilling device is a typical type thereof to drill efficiently a well conduit which is located at an extensive depth to a certain level of the stratum, to collect underground liquid resources including petroleum, natural gas, or geothermal vapor. For the aforementioned type of drilling device, it is indispensable to adapt the controlling device to be equipped at the distal end portion of said drilling device to control the moving direction of the drill bit so that the drilling bit can deviate when it faces a hard rock plate, resulting in the drilling operation proceeding efficiently without any undesired interruption. Furthermore, in a case when the drilling direction misses its aiming direction due to unexpected causes, it is also necessary to employ a controlling device at the distal end portion of the drilling device to correct the drilling direction to the original target direction.
Conventionally, several controlling mechanisms which are adapted to the rotary type drill bit have been proposed to correct the drilling direction, including those disclosed in Japan Patent Application Laid-Open No. Sho 57-21695, Japan Patent Application Laid-Open No. Sho 57-100290 and Japan Patent Application Laid-Open No. Sho 58-210300. However, the controlling mechanism disclosed in any one of the aforementioned patents is unable to control the drilling direction in all directions. Moreover, the controlling mechanism in said prior arts was complicated. These are disadvantages associated with the conventional types of devices for controlling the drilling direction.
Recently, another controlling, mechanism has been proposed in a disclosure of the Japan Patent. Application Laid-Open No. Hei 4-76183. The proposed mechanism consists principally of a plurality of the hollow-type harmonized reduction gear, a plurality of the eccentric rotating component equipped with an eccentric hollow portion which is connected to respective outputs of said hollow-type harmonized reduction gear and rotates in an eccentric manner with respect to a rotating shaft of each reduction gear, and a rotating shaft for the drill bit which is equipped at the drilling device in such a manner that said drill bit is inserted through the hollow portion of said hollow-type harmonized reduction gear and the eccentric hollow portion of the eccentric rotating component. The above structures enable the rotating shaft to change direction and location approximately along the direction of a central axial line of the shaft due to a restricting action of the inner peripheral surface of the eccentrically rotating eccentric hollow portion.
Furthermore, yet another controlling mechanism (Japan Patent Application Laid-Open No. Hei 5-149079) has been proposed. The proposed controlling mechanism comprises (1) first and second hollow-type harmonized reduction gears which are provided co-axially to each other, (2) a first ring-formed component which is located in a co-axial manner with respect to said first hollow-type harmonized reduction gear and rotates by said reduction gear, and (3) a second ring-formed component which is coaxially located with respect to said second hollow-type harmonized reduction gear and rotates by said reduction gear. Ring-formed end portions of said first and second ring-formed components overlap each other to intake a relative rotation possible. The end region of the thus overlapped portion is defined at the slant surface which is inclined with a certain angle. A rotating shaft for the drilling bit is inserted through a hollow portion of said first and second ring-formed components. By rotating relatively these first and second ring-formed components, a deflection can be provided along a certain direction on the rotating shaft.
Moreover, still another controlling mechanism has been proposed in Japan Patent Application Laid-Open No. Hei 5-202689, as seen in FIG. 16, which consists of (1) a cylinder-type housing 601, (2) a first ring-formed component 602 which is rotatably supported on a circular inner peripheral surface of the cylinder-type housing 601 and is provided with a circular inner peripheral surface which is eccentric with respect to said cylinder-type housing 601, (3) a second ring-formed component 603 which is rotatably supported on a circular inner peripheral surface of the first ring-formed component 602 and is provided with a circular inner peripheral surface which is eccentric with respect to said circular inner peripheral surface, and (4) hollow-type harmonized reduction gears 604,605 which rotate the aforementioned first and second ring-formed components 602,603 along their central axes. Having with the above structures, an amount of the eccentricity of the circular inner peripheral surface of the first ring-formed component 602 with respect to the cylinder-type housing 601 is set to be equal to the amount of the eccentricity of the circular inner peripheral surface of the second ring-formed component 603 with respect to the first ring-formed component 602. A rotating shaft 607 having a drill bit 606 at its distal end portion is connected to the second ring-formed component 603 in order to move along with a center portion of the circular inner peripheral surface of the second ring-formed component 603. Moreover, the rotating shaft 607 can be positioned with respect to a fulcrum bearing 608 as a fulcrum point by rotating, respectively, the first and second ring-formed components 602,603.
With all of the aforementioned controlling devices for the drilling direction of drill bits, since the fulcrum point of the deflection of the rotating shaft is located at the upper supporting mechanism for the shaft of the controlling device for the drill bit, there is a risk of fracture due to an excess bending stress which would be caused by the deflection provided at the rotating shaft.
In the above drills, if the deflection, which is subjected to the rotating shaft when the drill direction is deviated, is absorbed by providing a universal joint at the location at which the maximum bending stress takes place on the rotating shaft, then the damage on the rotating shaft due to the excess bending stress can be prevented.
Furthermore, it is necessary to protect the device for controlling the drilling direction from high temperature and high pressure hostile environment, since the drills are normally utilized in the area close to the bottom of oil or gas well conduits. Moreover, the lubricant oil, which is filled and sealed in a ring-shaped space defined with the cylinder-type housing being provided on the outer peripheral surface of the rotating shaft, is required to be sealed in a water-proof manner by sealing materials which are mounted at both ends of said cylinder-type housing.
With the conventional types of drills, the lubricant oil is filled and sealed inside the cylinder-type housings at ambient pressure and temperature on the ground level. When the drills are used in the bottom portion of well conduits, the lubricant oil will be indirectly exposed to high temperature and pressure. Hence, changes in pressure due to volume expansion will take place. Under these circumstances, if the pressure difference with the pressure of the surrounding muddy water exceeds the threshold pressure difference at seals which are located at both ends of the cylinder-type housings, the lubricant oil will leak out, or the muddy water will leak in. These might cause the controlling device to be inoperative.
Conventionally, a double seal mechanism has been employed as a sealing device between the cylinder-type housing and the rotating shaft, as seen in FIGS. 4a and 4f, disclosed in Japan Patent Application Laid-Open No. Sho 57-21695 (US 6/158948).
Although the direction and magnitude of the deflection to which the rotating shaft is subjected can be determined by the position of the rotating angles of the first and second circular components in the aforementioned types of devices for controlling the drilling direction, such a detecting mechanism was not described in said Japan Patent Application Laid-Open No. Hei 5-202689. Furthermore, said Japan Patent Application Laid-Open No. Hei 5-202689 employed a pulse-counting method (normally using a photo sensor or an eddy current sensor) by which, as seen in FIG. 17(a), a gear 702 is provided at the surface of the rotating body 701; and pulses, shown in FIG. 17(b), which detect the number of gears passing through during the rotation, are counted by using a sensor 703.
In summary, the devices for controlling the drilling direction described in Japan Patent Application Laid-Open No. Hei 4-76183, Japan Patent Application Laid-Open No. Hei 5-149079 and Japan Patent Application Laid-Open No. Hei 5-202689 exhibit the following technical problems.
(A) The thrust bearing, which bears the bit load, functions as a supporting mechanism for an upper rotating shaft of the device for controlling the drilling direction, and the bit load acts up to this location of the rotating shaft.
(B) Although the direction and magnitude of the deflection of the rotating shaft can be determined by knowing the rotating angular position of the first and second ring-formed components, it is difficult to maintain the original reference point for detecting the rotating angular position if a conventional type of pulse-counting method (normally using a photo sensor or an eddy current sensor) is employed. Moreover, it is more difficult to detect the rotating angular position with a satisfactory accuracy under the hostile environment at the bottom portion of the well conduits where the high temperature and pressure exist several hundreds or thousands of meters underneath the ground surface, although it could be achieved by adjusting the measuring accuracy on the ground.
(C) The fulcrum of the deflection of the rotating shaft functions as a supporting mechanism for the upper shaft of the device for controlling the drilling direction, resulting in the distance from the fulcrum to lower sealing mechanism becoming longer, and the magnitude of the eccentricity of the shaft at the lower sealing portion will become larger when the rotating shaft deflects. Accordingly, the structure of the sealing mechanism will become more complicated and the design for the sealing mechanism will become more difficult. Furthermore, the bending angle of the rotating shaft can not be made large due to the restriction from the sealing mechanism per se.
(D) The double eccentric mechanism supports the rotating shaft right above the drill bit. Hence the vibration during the drilling operation will transfer directly and instantaneously to the eccentric mechanism. This might cause a problem with regard to the structural integrity.
As a result, since the conventional type of controlling device controls the drilling direction by using the lateral load of the drill bit, then the quantity of lateral load of the drill bit will be extensively altered by the changes in the bit load due to the weak rigidity of the rotating shaft. In the worst case, the drill bit might turn to the opposite direction from the desired direction. This is an another major disadvantage associated with the conventional types.
Furthermore, the universal joint, which is utilized in the conventional type of devices for controlling the drilling direction, connects two eccentric driving shafts that are employed for driving the rotating machines and transfers only the rotating force. Unfortunately, any type of universal joint which can be utilized in locations where a fluid is flowing inside such drill pipes is not yet known.
Moreover, the double ring seals, which are located between the cylinder-type housing and the rotating shaft in the conventional type of devices for controlling the drilling direction, can not only respond to the changes in pressure of the lubricant oil which is filled and sealed between cylinder-type housing and the rotating shaft in the device for controlling the drilling direction of the drills, but also can not follow the changes in displacement along a direction perpendicular to the shaft axis of the rotating shaft when the drilling direction is required to change. Furthermore, the aforementioned type of sealing mechanisms exhibits a lower endurance due to the sliding movement of the displacement along the direction perpendicular to the shaft axis and the leaking-out of the lubricant oil and leaking-in of the muddy water can not be prevented.
Furthermore, the pulse-counting method to detect the position of the rotating angle of the first and second ring-formed components which are equipped in the device for controlling the drilling direction possesses the following technical drawbacks.
(a) It can only detect the position if the distance between the detecting sensor and the object is within several millimeters. In particular, the photo sensor is prone to be degraded due to the contaminated lubricant oil, resulting in a malfunction or a disability of the detection.
(b) An additional sensor, which is exclusively used for detecting the original reference point for the controlling purpose, is needed, causing a more complicated program for the angle detection.
(c) Although it is easy to control the original reference point on the ground level, it will become difficult to maintain said original reference point and nearly impossible to perform a satisfactorily accurate detection under the high temperature and pressure several hundreds or thousands of meters underneath the ground surface.
(d) Since the eddy current sensor is susceptible to being influenced by the noises due to the high frequency signals, it will be nearly impossible to conduct a accurate detection satisfactorily for cases of oil drilling operations by which the cable length between the sensor and the controlling unit could be on the order of several hundreds or thousands of meters under the ground level.
All of the foregoing have resulted in a requirement for the device of the present invention whose primary objective is to provide a device for controlling the drilling direction of the drill by which the positions of the rotating angles of the first and second ring-formed components can be detected with a satisfactory accuracy at the bottom portion of well conduits under high temperature and pressure. This means that (i) the magnitude of the displacement along the direction perpendicular to the axial direction of the rotating shaft at the lower sealing portion can be minimized, (ii) the adverse action of the bit load and vibration during the drilling operation on the eccentric mechanism portion--which is a relatively weak structure--can be controlled, (iii) and the rigidity of the rotating shaft above the drill bit can be enhanced.
The second objective of the present invention is to provide a hollow universal joint for drills by which the deflection generated at the rotating shaft can be released by said device for controlling the drilling direction, and the flowing-out of the muddy water, which is flowing inside the rotating shaft, can be prevented.
The third objective of the present invention is to provide pressure-equalizing equipment and sealing equipment for the device for controlling the drilling direction, by which leaking-out of the lubricant oil which has been filled and sealed in the said controlling device and leaking-in of the muddy water can be prevented for a long period of time.
The fourth objective of the present invention is to provide angle-detecting equipment by which (regardless of the distance between the detecting sensor and the object and the presence of contaminated lubricant oil that has been filled and sealed into said device for controlling the drilling direction) an absolute value of the angle from the original reference point of the first and second ring-formed components can be accurately and stably detected under the presence of hostile environments including the high temperature and pressure at the bottom area of the well conduits, which are normally located at several hundreds or thousands of meters underneath the ground surface ground; detection of the original reference point and angle can be achieved by using only one sensor; and the undesired attenuation due to length of cables between the sensor and the controlling device and noises will hardly influence the detection accuracy.